1. Field of the Invention
The present invention relates to a fixing apparatus that fixes a toner image formed on a recording sheet and an image forming apparatus including the same.
2. Description of the Related Art
A fixing apparatus of this type is applied to an image forming apparatus that uses an electrophotographic method, an electrostatic recording method, a magnetic photographic method, or the like. Such a fixing apparatus heats and presses a recording sheet (such as plain paper, electrostatic recording paper, or photographic paper) onto which a toner image has been transferred, the recording sheet being sandwiched between a pair of fixing rotation members (belt, roller), and thereby fixes the toner image on the recording sheet.
In such a fixing apparatus, the circumferential surface of a fixing rotation member may become smeared due to toner and the like, and thus it is necessary to clean the circumferential surface of the fixing rotation member using a blade, felt, a web sheet, or the like. Further, if the processing speed of the image forming apparatus is fast, and the number of sheets to be printed per unit time is large, smearing on the fixing rotation member of the fixing apparatus increases, and thus the smearing cannot be completely removed by cleaning the fixing rotation member using a blade or felt. Thus, cleaning using a web sheet is often adopted.
For example, in the fixing apparatus disclosed in JP H8-185074A (hereinafter, referred to as Patent Document 1), a web sheet is fed out from a feed roller and taken up by a take-up roller, and the web sheet is pushed against a fixing roller during the feeding-out and taking-up operation, thereby cleaning the circumferential surface of the fixing roller. Further, the take-up roller is driven by a motor so as to rotate at a low speed, thereby taking up and feeding out the web sheet.
In the fixing apparatus disclosed in JP H9-197884A (hereinafter, referred to as Patent Document 2), a web driving solenoid is used in order to drive a take-up roller that takes up a web sheet. Moreover, the amount by which the web sheet is taken up is adjusted according to image density.
However, even if smearing on a fixing rotation member can be effectively removed by adopting cleaning using a web sheet, if a motor or a solenoid for rotating the web sheet take-up roller at a low speed is provided as with the case of the fixing apparatuses disclosed in Patent Documents 1 and 2, this results in an increase in power consumption and a rise of cost compared with using a blade or felt.
On this account, it is conceivable to use a motor for rotating a fixing rotation member as a motor for rotating a web sheet take-up roller. In this case, the rotational speed of the web sheet take-up roller is very slow, compared with the rotational speed of the fixing rotation members, and thus a great speed reduction ratio will be necessary.
However, for example, in a configuration in which the distance between the shafts of the fixing rotation members is changed according to the thickness of a recording sheet, the positional relationship among the shaft of the web sheet take-up roller and the shafts of fixing rotation members also changes. Thus, it was difficult to constitute a power transmission mechanism that can rotate both a fixing rotation member and the web sheet take-up roller using one motor, and can sufficiently increase the speed reduction ratio of the web sheet take-up roller.
Further, in the case where the motor for rotating a fixing rotation member is used as a motor for rotating the web sheet take-up roller, it was difficult to adjust the amount by which the web sheet is taken up since the fixing rotation members and the web sheet take-up roller are caused to operate in conjunction with each other. For example, if the process speed is switched and set according to a color image or a monochrome image, the amount by which the web sheet is taken up also changed, and thus the take-up amount was not able to be accurately set.